It's not about following formalities or the rules of the house.
Let's say you can't stand the personality of your wife's brother. He whines. He talks ill about other people behind their backs. Is a little rich spoilt brat and just complains about everything and is essentially a snob. You need to deal with that person for a few weeks because they are in town for something and they are staying with you guys as your wife is his sister.
How do you, as a male, deal with annoying in-laws staying over, especially when the annoying person is another adult male in your domain?
Most "meN" would ignore it. As women should either if they have annoying female in laws.
X2...whatever. same ish.